There is known a vehicular hybrid drive system provided with an engine, a first electric motor connected to the engine, and a second electric motor connected to drive wheels. There has been proposed a technique to suitably cooling an electric motor depending upon a selected drive mode of such a vehicular hybrid drive system. Patent Document 1 discloses an example of a cooling device for practicing the technique. This cooling device is configured to control a delivery amount of an oil pump such that an amount of a working oil to be supplied to the electric motor is larger in a drive mode of the hybrid drive system in which a vehicle drive force generated according to a selected output characteristic at an operation amount of an accelerator pedal is larger than in a drive mode in which the vehicle drive force according to selected another output characteristic is comparatively small, so that the amount of the working oil to be supplied to the electric motor for cooling the electric motor can be increased with an increase of the required vehicle drive force, making it possible to sufficiently cool the electric motor depending upon the selected drive mode of the hybrid drive system.